1. Field of the Invention
The present invention relates to a printed circuit board (PCB) working machine, and more particularly to a PCB working machine for preparing a printed circuit board (PCB) by forming a circuit pattern on a copper foil substrate, for example, in accordance with data described by, for example, a computer aided design (CAD).
2. Description of the Related Art
It is required to experimentally produce the PCB, on which suitable electronic circuit is formed, precisely and speedily with low cost for the development of electronic equipments and the manufacturing of the electronic equipments which are not objects for mass-production.
However, when the PCB is experimentally produced, some optical processes and chemical processes are to be required, so that even in the preparation of less number of PCBs for testing, it is required to prepare a circuit pattern, which includes a complicated working, thus being inconvenient.
In order to overcome such inconvenience, there may be proposed a PCB working machine for cutting out a desired circuit pattern by effecting a cut-working to a copper foil substrate as a PCB material (called hereinafter PCB substrate). Such a PCB working machine is equipped with a working table for absorbing and securing the PCB substrate to carry out a desired cut-working, and above the working table, there is disposed a spindle which is movable under being controlled in X-axis and Y-axis directions by X-axis and Y-axis driving apparatuses and which is elevated vertically by a Z-axis driving apparatus. A desired cutting tool is detachably mounted to the spindle through a collet chuck. On the other hand, below the working table, there is disposed an index table for holding various cutting tools and exchanging the cutting tools in association with the lowering movement of the spindle. A float head formed with an air jetting port is also formed on an outer peripheral side of the spindle to be vertically movable in such a manner that the front end portion of the cutting tool fixedly clamped to the collet chuck projects from the float surface of the float head by a predetermined projection amount, the cutting tool sticks the PCB substrate by a predetermined depth, and an air layer is formed between the float surface of the float head and the PCB substrate by the air jetted from the air jetting port, whereby the sticking amount of the cutting tool is maintained constant and the gap between the float surface and the PCB substrate is also maintained.
In the PCB working machine of the structure described above, a cut width of the PCB is adjusted in such a manner that a desired PCB substrate is positioned on the working table and then absorbed and secured, the spindle is lowered by the Z-axis driving apparatus, and the projecting amount of the cutting tool is adjusted so as to accord with a desired sticking depth. Thereafter, the X-axis and Y-axis driving apparatuses are driven under the control thereof in accordance with the desired circuit pattern and then moved while rotating the spindle. In such a manner, the copper foil layer and an insulative substrate are cut to thereby form the desired circuit pattern.
During this circuit pattern forming operation, for example, after the cut-working in the X-axis direction of the PCB substrate, it is moved in the Y-axis direction by an amount corresponding to a cut amount, and a next cut-working again in the X-axis direction is performed. By repeating these workings, the cut-working to an entire surface of the PCB substrate can be done. In the cut-working in the X-axis direction, when the cutting tool is positioned to a position corresponding to a circuit pattern portion which is not required to be cut, the spindle is moved upward to a cutting position including no circuit pattern. Thereafter, the spindle is again lowered to continue the cut-working.
However, in the above mentioned PCB working machine, since it is necessary to move up and down the spindle in accordance with the circuit pattern of the PCB substrate, the spindle must be moved up and down very frequently, resulting in the positional shifting of the spindle during these up and down movements, and in an adverse case, a high precision working will not be expected, thus providing a significant problem. Furthermore, since the spindle and its associated members have relatively heavy weight, each elevational movement of the spindle requires much time which damages a speedy cut-working, thus also providing a problem.
Still furthermore, in a case where it is required to exchange a cutting tool held by the collet chuck of the spindle, the spindle is lowered to a portion near the index table, so that the exchanging of the cutting tool cannot be speedily carried out and, moreover, the large lowering amount, i.e. distance, of the spindle makes enlarged and complicated an elevating mechanism for the spindle, and thus, the spindle is made heavy, and when the spindle is moved fast at the working time thereof, it may be shifted and the cut-working at high speed with high precision will not be expected, thus also providing a problem.
Still furthermore, when the cutting working of the cutting tool advances, there may be caused a case in which the float surface of the float head takes a position riding on both a cut surface and a surface to be succeedingly cut. In such a case, a gap between the float surface of the float head and the cut surface is formed larger than a gap between the float surface and the surface to be succeedingly cut, resulting in that the air pressure from the air jetting port is made lower to the cut surface and, hence, there may be caused a case where the float surface is lowered or inclined. Because of this reason, it becomes difficult to ensure a constant gap between the float surface and the PCB substrate, and accordingly, it becomes impossible to constantly maintain the sticking amount of the cutting tool, and a precise cut-working with the constant width maintained cannot be expected, thus also providing a problem.